This application claims priority of Korea patent Application No. 10-2000-0086902, filed on Dec. 30, 2000.
(a) Field of the Invention
The present invention relates to a fuel injector of a vehicle engine, and more particularly, to a high-pressure, direct-injection fuel injector having a swirl generator for imparting a desired level of swirling motion to the fuel as it exits the injector.
(b) Description of the Related Art
Generally, because a fuel injector of a GDI (Gasoline Direct Injection) engine injects fuel into a combustion chamber directly, it operates under high pressure. Also, the fuel injector of the GDI engine (hereinafter called a GDI injector) is required to inject a specific amount of fuel for a specific period. Moreover, in the process of injecting fuel there are many parameters to be considered, such as injection range, injection angle, size of fuel droplets, evaporation level and the like, and because the fuel injector is installed in the combustion chamber it has restrictions of space and temperature. Recently, several types of GDI injectors have been proposed, and among them a swirl type injector, which has a swirl generator, is widely adopted. The swirl generator imparts a swirling motion to the fuel as it exits the injector. Therefore, fuel dispersibility increases and fuel is prevented from being directly sprayed against a piston or a cylinder liner, and the fuel is well mixed with air.
But in the GDI engine it becomes necessary to change a level of a swirl flow component according to driving conditions. That is, when stratification combustion in the latter part of compression is performed at a low load range, a high level of swirl motion is required because the injection range should be relatively small, and fuel should be mixed with air quickly to get a suitable air-fuel mixture around a spark plug in a small combustion volume. On the other hand, when in a high load range, fuel is injected at an intake stroke or an early state of compression, and a low level of swirl motion is required because there is a large volume for burning and relatively sufficient time for mixing.
A conventional GDI injector is provided with a swirl generator around a needle being located in a nozzle tip. If the needle is operated such that a fuel passageway is formed, fuel passing through an inclined passageway of the swirl generator has a constant level of swirl motion.
Because the conventional GDI injector has a constant level of swirl motion under constant injection pressure, the conventional GDI injector has the same injection range and air-fuel mixing level in both uniform combustion and stratification combustion, and therefore optimal driving control is almost impossible.
The present invention has been made in an effort to solve the above problems. It is an object of the present invention to provide a GDI fuel injector having a swirl generator around the needle of the nozzle tip, which can change a level of a swirl motion component of injected fuel.
To achieve the above object, a GDI fuel injector has a nozzle body, a needle member centrally located within a nozzle body such that a fuel passageway is formed between the needle and the nozzle body, and a swirl generator, the swirl generator comprising:
an inner case having a cylindrically-shaped body having an opening from the upper end to the bottom end along its longitudinal axis, and several equally and angularly spaced lobes;
an outer case having a cylindrically-shaped body having an opening from the upper end to the bottom end along its longitudinal axis, and several equally and angularly spaced grooves 36 inside the body 34, of such size and shape so as to receive the lobes of the inner case; and
an inner case rotator, one end of which is fixedly connected to the inner case such that the inner case can be axially rotated by axially rotating the inner case rotator, the other end being provided with a grip.